U.S. Great Lakes thawing earlier.

• Author: Mastny, Lisa
• Position: ENVIRONMENTAL INTELLIGENCE - Brief Article

The Great Lakes region of the United States, home to the largest concentration of fresh water on Earth, is thawing earlier each spring, according to findings reported in the August 20 issue of New Scientist. Scientists with the University of Wisconsin-Madison (UW-M) found that on 56 of 61 lakes studied the spring thaw showed an earlier trend, occurring two days sooner on average each decade between 1975 and 2004.

The date of ice break-up has "marched northward 100 kilometers per decade" since the mid-1970s, said Barbara Benson of UW-M's Center for Limnology. The team studied the timing of break-up on lakes in Minnesota, Wisconsin, Michigan, New York, and Ontario, gathering information from government databases, newspapers, lake associations, and local residents.

The study notes that although the earlier thaw has been happening since 1846, the rate of change has accelerated and is now more than three times as fast as before 1975. Since the mid-1970s, the average global air temperature has risen by 0.4 degrees Celsius, suggesting a link to a...